I have an idea for an extremely crackpot engine design for a future society I may incorporate into my story.

What would happen is individual antihydrogen molecules injected into the center of carbon fullerene molecules using the combined electron clouds of the atoms to repel the antimatter into the center of the fullerene spheres so they don't touch anything. This keeps the antimatter from annihilating anything until needed for use.

Now to ignite the engine an electric spark is used to ignite the fullerene, releasing the antimatter creating annihilation. The annihilation would create an explosion that drives a piston turning a crankshaft.

Assuming a plentiful antimatter supply and the manufacturing to make a chamber capable of absorbing the impact and produce this sort of fuel in large numbers is this at all feasible?

$\begingroup$This is all well and good, but why would you want to send your piston into outer space?$\endgroup$
– Justin Thyme the SecondMar 16 at 1:51

$\begingroup$@JustinThymetheSecond I'm assuming the piston and the chamber are built with the right amount of engineering technology to conatin the force of the explosion.$\endgroup$
– EfialtesMar 17 at 20:13

1

$\begingroup$The idea of a piston engine is that the piston first compresses the gas in the chamber to extremely high compression ratios, and then the mixture in the chamber is 'ignited' by some mechanism that causes extreme and sudden expansion. The antimatter is the 'spark' that immediately decomposes the super-compressed air in the cylinder, causing rapid expansion. By the nature of the engine, the piston is allowed to move under this pressure. Even in a conventional engine, this movement is so dramatic that pistons have been known to fly through the engine block and become airborne.$\endgroup$
– Justin Thyme the SecondMar 17 at 21:46

$\begingroup$The more I think about this, the more I ponder that the piston engine is the wrong format. My money would be on a rotary, or Wankel-type, engine. No sudden reversals of motion, as the pistons would go through.$\endgroup$
– Justin Thyme the SecondMar 19 at 2:44

3 Answers
3

Antimatter reactions are quite awkward things to make use of on a small scale, or in the presense of delicate things like people or electronics.

About a third of the energy liberated by the reaction comes out in the form of gamma rays. These won't be absorbed well by the fuel you're burning, but will heat up the engine block pretty effectively.

Most of the rest of the two thirds of the energy released comes out in the form of charged pions. Some of these will do interesting things to your fuel and heat it up (which is good!) but more are likely to just heat up your engine block (which is quite bad) and depending on how much shielding you have plenty more will just sail out into the space around your engine and decay into gamma rays out there. You'll need a decent amount of radiation shielding, and a decent amount of cooling. This is all heavy and inconvenient.

Can I make an alternative suggestion?

I give you... the antimatter train.

The engine is basically a solid core antimatter rocket. A cylinder of some dense, high-melting point metal filled with holes for water to run through. You liberate your antimatter in the centre of the cylinder, and most of the energy of the reaction products will go to heating up the cylinder which will also do a reasonable job of shielding spectators from deadly radiation.

The antimatter rocket needs to operate at a couple of thousand kelvin to be worthwhile, but the train can get away with merely enough to generate superheated steam. Then you just use that to run a conventional piston engine, or if you're being boring, a steam turbine. Now all you need is a very small fuel tank and a generous supply of water and you're good to go.

$\begingroup$Welcome to Worldbuilding.SE! We're glad you could join us! When you have a moment, please click here to learn more about our culture and take our tour. And well-done for a first answer! You provided an explanation of why the OP's desire would be difficult (called a Frame Challenge) and then provided an alternative. Great!$\endgroup$
– JBHMar 15 at 20:49

A company by the name of General Fusion has a somewhat similar design for a nuclear fusion reactor. It is possible that the matter/antimatter reaction will create a form of harmful radiation that would need to be dealt with, or at least contained inside the reaction chamber. I would argue that attempting to store antimatter is not the best approach, as a failure of the containment vessel would be catastrophic. A better approach would be to generate the antimatter on the fly, expose it to its matter counter part, and then use the resulting explosion to power your pistons. You could also use the heat generated by the annihilation process to boil water and create steam similar to nuclear reactors.

Fullerenes are not able to contain antimatter. They are electrically neutral, to contain antimatter you either need to have it charged and use a ion trap, or freeze it and levitate it, to keep it from interacting with matter.